1. Technical Field
The present invention is directed to imaging sensors and the associated imaging devices. In particular, the invention is directed towards a more compact imaging sensor providing for more efficient operation of an imaging device and providing for denser pixel structure on the imaging device.
2. Related Art
Conventional image technology usually places most acquisition and control elements near the surface of a wafer. A pixel structure occupies an area on the wafer or integrated circuit (IC) chip. This area is divided between area used for elements actually acquiring the image and elements controlling the functionality of the image sensing element.
Typically, a light sensing element, such as a photodiode, takes up an area on a surface of the IC chip housing the imaging device. The area of the diode on the surface of the IC chip generates a signal indicative of the light striking the area.
However, the total pixel structure requires control circuitry for controlling the actions of the overall photodetector and the transmission of the signal from the photo-sensing element to the remainder of the imaging device. These control functions include select circuitry, amplifier circuitry, and reset circuitry. This control circuitry is typically made up of transistors and metal interconnect lines that take up space on the surface of the IC chip.
Thus, the total area for a single image detector cannot be used for light detection. The ratio of the light sensing surface to the total area required for the light detector structure including the detection circuitry and the control circuitry is known as the fill factor. Conventional imaging sensors generally have a low fill factor ratio. For a typical conventional sensor, the fill factor may range from 20% or so to 40% in higher end sensors.
With lower fill factors, the number of pixels per imaging device is lower. As such, fewer sensors may be placed in a given area, and the density of the light sensors on the IC chip is decreased.
With higher densities of imaging sensors on an IC chip, the total size of an imaging device may be reduced with the same number of pixels. Or, higher granularity or sensitivity may be obtained by putting more imaging sensors in a constant area.
Additionally, greater color clarity and color discrimination may be achieved with higher pixel or imaging sensor density. In some conventional color imaging devices, a coating may be used on an individual imaging element to selectively activate that imaging element for a particular wavelength of light.
In a red-green-blue (RGB) color scheme, for example, a single pixel or light sensor may be manufactured to be responsive to blue light. Other adjoining or nearby pixels or light sensors are manufactured to be responsive to red and green light, respectively. As for the pixel that is activated solely by blue light, the red and green components for the blue pixel may be estimated by using values of nearby pixels activated by red and green light, respectively.
Thus, for example, assume a fill factor of 25% for an older imaging sensor. If the fill factor can be improved to one of 75%, an imaging sensor could directly measure the red, green, and blue components of a target image in the area of an older single pixel, which also needs estimations from other adjoining pixels for missing color components. Thus, the color clarity of a target image may be improved with denser image sensors without sacrificing granularity. Correspondingly, an image of a finer granularity can be derived from a higher fill factor.
Thus, when the fill factor can be raised, more efficient imaging devices may be constructed. A higher fill factor means that the pixel structures or the individual imaging sensors may be placed closer together. Thus, a higher fill factor leads to having higher density of imaging devices per wafer. This leads to sharper images due to more imaging sensors, or to smaller IC chips for the same sensitivity of imager.
Many other problems and disadvantages of the prior art will become apparent when schooled in the art after comparing such prior art with the present invention described herein.
Various aspects of the invention may be found in a light imager. The light imager is contained on an integrated circuit (IC) chip or die. The light imager has one or more light sensors. Each of the light sensors has a light sensing element and control circuitry.
In the individual light sensors, the control circuitry is communicatively coupled to the light sensing element and controls the functions of the light sensing element. The control circuitry is substantially disposed within the IC chip, freeing the additional top area of the die for the light sensing elements.
In an alternative embodiment, the light imager has a processing circuitry. The processing circuitry is communicatively coupled to the one or more light sensors. The processing circuitry may also have an application program executing on it.
The placement of the control circuitry within the IC chip allows for a higher fill factor associated with each light sensor. As such, the fill factors of the light sensors can be greater than 50%.
The control circuitry of the invention may be such things as a reset transistor or an amplifier transistor. These components may be manufactured within the IC chip.
In another embodiment of the invention, a light imager is contained on an integrated circuit die. The light imager has one or more light sensors, the light sensors having a fill factor, or a ratio of the area used for collection of light to the total area of the light sensor.
The light sensors have a light sensing element and a control circuitry. The control circuitry is communicatively coupled to the light sensing element, and controls the operation of the light sensing element. Additionally, at least some of the control circuitry is disposed within the integrated circuit die.
In another exemplary embodiment of the invention, the light imager is contained on an integrated circuit chip. The light imager has one or more light sensors. The light sensors have control circuitry coupled to the light sensing elements.
Each of the light sensors is disposed on a corresponding sensor area on the integrated chip. The sensor area has a light sensing area, where the light is collected by a light sensing element. The light sensing area makes up at least 50% of the sensor area.
The light sensor may also have a processing circuitry communicatively coupled to the one or more light sensors. Additionally, the light sensor may also have an application program executing on the processing circuitry.
Aspects of the invention may also be found in a light sensor. The light sensor is disposed on and within an integrated circuit chip. The light sensor has a fill factor, meaning the ration of the area used for light collection to the total area of the sensor. The light sensor has a light sensing element and control circuitry. The control circuitry is communicatively coupled to the light sensing element and controls the output of the light sensing element. The control circuitry is disposed substantially within the integrated circuit chip. As such, the fill factor of the light sensor is at least 50%. Portions of the control circuitry that may be disposed within the IC chip are a reset transistor and an amplifier transistor, among others.